Redis

About Configuring the Redis Server

The configuration settings for the Redis server are controlled through the conf file that is specified when installing the service. You can change settings by modifying the file and restarting the service to apply the changes. You can also use the CONFIG GET and CONFIG SET commands from a Redis client to view or alter the server configuration.

Note: The conf file does will not be updated with the changes settings that occur at run time. After making changes to the conf file, be sure to restart the service.

Configure Server and Ports

By default, the Redis server runs on TCP Port 6379.

  • If the GE Digital APM server and the Redis server are on same machine, then connections are allowed from the local server.
  • If the GE Digital APM server and the Redis server are on different machines, then Port 6379 must be accessible between the Client and the Server. Any firewalls between the systems must be configured to support traffic over this port. The default port is changed in the conf file to 6379 by adjusting the port value.

Configure Secure Access

It is recommended to always use Redis in an environment in which the network and the Redis server are secured.

  • If the GE Digital APM server and the Redis server are on same machine, then Redis can be secured by blocking external access to the network port (port 6379), allowing connections only from the local server.
  • If the GE Digital APM server and the Redis server are on different machines, you can secure the access by:
    • Configuring Redis to use a password.
      Note: By default, Redis is configured without a password.

      When using a password on the Redis server, you must configure the connection string to include the password.

      1. On the GE Digital APM Server, access the folder C:\ProgramData\Meridium, and then, in an application that you can use to modify XML script (for example, Notepad), open the file MeridiumAppSettings.xml.
      2. Within the <cacheServiceUrl> setting, change the default value localhost to localhost,password=<Redis password>, where <Redis password> is the password for the Redis server.
      Note: The password in the .XML file can be encrypted by running MeridiumCachePasswordUtility.exe from a command prompt, passing in C:\ProgramData\Meridium\MeridiumAppSettings.xml as a command line parameter.

    • Setting up the firewall on the Redis server to only allow connections from the GE Digital APM servers.

Note: If Redis is configured on a separate server and network transmissions are across an unsecured/open network, then it is recommended to use third-party software (e.g., Stunnel) to enable SSL communication between systems.

Standard Deployment Architecture

By default, the standard single system deployment architecture includes the Redis server on the same system as the GE Digital APM Server.

Set Up the GE Digital APM Server - Medium Cache Configuration

GE Digital APM Servers are set up either using a medium cache configuration or a high availability configuration.

About this task

Note:

In a standard deployment, the Redis server is on the same system as the GE Digital APM Server.

To configure GE Digital APM servers using medium cache configuration:

Procedure

  1. On the GE Digital APM Server machine, navigate to the folder C:\ProgramData\Meridium.
  2. Open the file MeridiumAppSettings.xml in an application that you can use to modify XML script.
  3. Within the <Cache Service> tag, make changes to the following Redis-specific settings.
    • The cacheType value should equal "redis".
      Note: The cacheType value “redis�? is supported for any customer implementations.
    • The default value for cacheServiceUrl is "localhost". If Redis is configured on different server using a non-default port, values should contain a comma separated set of values.
    • The default value for cacheTimeout is 1 day, or 1440 minutes.
    Note: The system will first check whether these settings are configured in the executable or web config file and, if they are not, it will then load them from the MeridiumAppSettings.xml file. GE Digital’s recommendation is to use the MeridiumAppSettings.xml file to ensure consistency across the installation and to give you the ability to change the settings for all of the services and websites in one place per server.

Install Redis - High Availability Configuration

GE Digital APM Servers are set up either using a medium cache configuration or a high availability configuration.

About this task

Note: By Default, GE Digital APM Installer performs these steps automatically for a standard install.

Procedure

  1. On the GE Digital APM Server machine, login as an administrator.
  2. Open a command prompt window.
  3. In the command prompt window, change to the directory where the file was copied.
  4. Enter the following command in the window: redis-server --service-install redis.windows.conf
  5. Press Enter on the keyboard.
    Redis is installed as a service.
  6. On the Windows Start menu, enter Services.msc in the search box.
  7. Press Enter on the keyboard.
    The Services window appears.
  8. Double-click on Redis service.
    The Redis service is now running on the GE Digital APM Server machine.

Setup GE Digital APM Server - High Availability Configuration

About this task

If GE Digital APM Servers are set up in a load-balanced configuration, then two Redis servers should be running, each on a separate system, with each GE Digital APM server/service configured to point to the separate systems. Redis servers can be configured either by Replication only Setup or by Automatic Fail-Over monitoring.

The first Redis server setup is used for caching. The second Redis server setup is used by GE Digital APM Scheduling Service to broadcast events to instances of GE Digital APM.

The following image illustrates how the Redis server setup used by GE Digital APM Scheduling Service communicates with instances of GE Digital APM over web socket protocol.

Redis can be configured with replication only. Replication only setup means that Redis will replicate data automatically to any configured slaves but in the event of a failure, an administrator must login and manually change a server to be master instead of slave.

A number of changes are needed in the Redis configuration file. To enable the Redis master-slave configuration:

Procedure

  • Steps: Changes to the Master
    1. Configure the save intervals.

      save 900 1

      save 300 10

      save 60 10000

    2. Configure the directory for the persisted data.
      heapdir "c:\\path_to_where_data_is_stored\\"
    3. Enable peristence.
      persistence-available yes
  • Steps: Changes to the Slave
    1. Configure the slave to point to the master IP address.
      slaveof <masterip> <masterport>
    2. Configure the slave priority to a lower value than the master.
      slave-priority 1
      Note: The default priority is 100. You should configure the first slave and set the priority to 1, then set the priority of the second slave to 2, and so on.
  • Steps: Automatic fail-over monitoring and configuration
    In this type of setup, the setup will automatically replicate any data changes from the master to the slave. Sentinel will then automatically detect a failure and re-configure the Redis slave to be the master in the event of a failure.
    Note: It is is recommended that Redis be configured in a master/slave setup with Sentinel.
    1. Install Sentinel using the Redis server executable file.
    2. Make changes to the Sentinel "Conf" file:
      redis-server --service-install sentinel.windows.conf --loglevel verbose --service-name Sentinel --sentinel
    3. Configure the port in the Sentinel "conf" file.
      Note: By default, the Redis server runs on TCP Port 6379. If using in a non-secure network then the port should be blocked from external access but be accessible from all other sentinels and all Redis servers. Sentinels should be 1 more than the number of slaves.
    4. To use GE Digital APM, Redis, and Sentinel in a High Availability Configuration:
      1. On the GE Digital APM Server machine, navigate to the folder C:\ProgramData\Meridium.

      2. Open the file MeridiumAppSettings.xml in an application that you can use to modify XML script (for example, Notepad).

      3. Within the <Cache Service> tag, make changes to the following setting:
        • cacheServiceUrl- This should contain connection details to the Redis server setup that will be used for caching. The servers are separated by a comma at the beginning of the connection string and should include the port number, if non-default ports are used.
      4. Within the <appSettings> tag, make changes to following settings:
        • useRedisBackplane : This should be set to true.
        • redisBackplaneUrl : This should contain connection details to the Redis server setup that will be used by GE Digital APM Scheduling Service. The servers are separated by a comma at the beginning of the connection string, and, if non-default ports are used, should include the port number.
      5. For each GE Digital APM Server in the high-availability configuration, repeat steps a through d.
    Note: All servers (GE Digital APM, Redis, and Sentinel) in a High Availability configuration must use the same password.

About Redis

Redis is a high-performance, NoSQL key-value database typically used for caching data to scale high-traffic websites. GE Digital APM uses Redis for caching purposes and to ensure a consistent shared cache among the various servers and services that make up a GE Digital APM installation.

If GE Digital APM servers are set up in a load-balanced configuration, then a separate Redis server is also used as an intermediate to broadcast events from the Meridium Scheduling Service to instances of GE Digital APM that are connected to different GE Digital APM Servers using the WebSocket protocol.

Redis is an open source software component licensed under the Three Clause BSD License.

More Details

Redis provides a basic Pub-Sub messaging infrastructure that allows the server to notify subscribed clients of changes or various events that occur on the server. The GE Digital APM uses this feature to notify servers/services when cached data has changed, caches expire, or caches are removed. This feature, along with the Meridium Notification Service, is used for change notification. Redis events specifically handle cached/static data such as metadata, while the Meridium Notification Service handles more dynamic changes such as Entity inserts/updates. Redis is used as an in-memory cache to store user session information, various types of metadata (e.g., family definitions, field definitions, security groups, etc.), and Catalog data.

Meridium Scheduling Service runs on each GE Digital APM Server in a load-balanced configuration. For a user session, an instance of GE Digital APM connects to one of the GE Digital APM Servers using the Websocket protocol, but the background job can run on any server in a load-balanced configuration. Meridium Scheduling Service sends the message to the Redis server, and the Redis server then relays the message to all GE Digital APM Servers. Finally, the GE Digital APM Server sends this message to the GE Digital APM instance connected using the WebSocket protocol.